Performance feed-forward thickness control method in tandem cold mill

ABSTRACT

The present invention relates to the field of strip cold rolling, and in particular to a thickness control method for strips in a tandem cold mill. Frame S 1  and one or more additional frames are selected as virtual indirect measuring instruments for the strip performance. A load cell is provided on the frames that are selected as the indirect measuring instruments for the strip performance, and deformation resistance fluctuation of the supplied materials of the frame S is calculated. Finally, the feed-forward adjustment amount of each frame is calculated. The present invention measures the deformation resistance of each section of the strip of the supplied materials through the selected frame, reducing the fluctuation of the thickness of the finished products of the strip and ensuring stable rolling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application represents the national stage entry of PCTInternational Application No. PCT/CN2013/075316 filed May 8, 2013, whichclaims priority of Chinese Patent Application No. 201210161787.0, filedMay 23, 2012, the disclosures of which are incorporated by referencehere in their entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates to the field of strip cold rolling, and inparticular to a thickness control method of strips in tandem cold mill.

BACKGROUND OF THE INVENTION

Thickness precision is one of the most important quality indexes forcold rolled strips. With the rise and development of industries likeautomobiles, aviation, household appliances, precision instruments,civil architecture, food cans, there are strict requirements on thethickness precision of cold rolled strips.

Tandem cold mill is one of the most complicated equipments with highestdegree of automation and meeting the strictest requirements on precisionin metallurgical industry, which, to some extents, represents the levelof technological development in steel industry. Thickness feed-forwardcontrol in tandem cold mill plays an important roll in ensuring thethickness precision of cold rolled strip finished products. Thethickness deviation of supplied materials is one of the significantcauses for the thickness deviation of cold rolled strip finishedproducts; therefore, the traditional thickness feed-forward control in atandem cold mill is performed by the thickness deviations of suppliedmaterials measured directly before frames.

The complexity of hot rolling process may thus result in performancefluctuation of the supplied materials, that is, the hot rolled products.The fluctuation thereof exhibits some degree of regularity. When asection of strip with said performance fluctuation enters each frame ofthe tandem cold mill, new thickness deviations may occur. Thus, it is ofgreat significance for improving the thickness precision control to doresearch on the thickness feed-forward control method in the case ofperformance fluctuation of strips.

In the current thickness feed-forward control in a tandem cold mill, thethickness deviations of supplied materials measured directly before theframes S₁, S₂ and S₅ are used for the feed-forward control. Theadjustment mechanisms used for feed-forward control are hydrauliccontrol systems of the frames S₁, S₂ and S₅, respectively, and theprinciple thereof is shown as FIG. 1. Feed-forward control is mainlyused for eliminating the instantaneous deviation, that is, when a largevariation of the supplied material at the entry of a frame takes place,the hydraulic control systems of the frame takes actionscorrespondingly, so as to substantially eliminate the thicknessdeviations before exiting the frame.

Due to the higher requirements from users on the thickness precision ofthe cold rolled products as well as the complexity of hot rolling, it isnecessary to take the effects of the performance fluctuation of thesupplied material on the thickness deviations of finished products intoconsideration. The direct measurement on the performance of suppliedmaterials before the tandem cold mill needs to add measuringinstruments. However, the current measuring instruments have lowprecision. Additionally, this method needs to increase the equipmentcost and corresponding maintenance personnel during manufacturing.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a performancefeed-forward thickness control method in a tandem cold mill, whichperforms the thickness feed-forward control by the deformationresistance force of supplied materials measured indirectly. The methodprevents the effects of performance fluctuation of supplied hot rolledproducts on the accuracy of thickness control during cold rolling, whichis of positive significance to guarantee the precision of the thicknessof finished products of the strip in the length direction of the entiresteel coil, reducing the fluctuation of the thickness of the finishedproducts of the strip and ensuring stable rolling.

The objective of present invention is achieved in such a way that aperformance feed-forward thickness control method in a tandem cold millcomprises the following steps:

step 1, selecting one or more frames as virtual indirect measuringinstrument(s) of strip performance, in which the frame S₁ must be avirtual indirect measuring instrument of strip performance, and athickness gauge is provided at the entry of S₁;

step 2, calculating the value of the deformation resistance fluctuationof supplied materials: providing a load cell on the frames that areselected as the indirect measuring instruments for the stripperformance, measuring the rolling force deviation ΔP_(i) caused by thedeformation resistance fluctuation of the frame S_(i) via the load cell,then calculating the value of deformation resistance fluctuation Δk_(i)of supplied material of the frame S_(i) according to the followingformula 1:

$\begin{matrix}{{{\Delta\; k_{i}} = \frac{\Delta\; P_{i}}{Q_{i}}},} & (1)\end{matrix}$where Q_(i) is the influence coefficient of the deformation resistanceon the rolling force of the frame S_(i), which is an empiricalcoefficient and obtained through experiments;

step 3, calculating the feed-forward adjustment amount for each frame:calculating the feed-forward adjustment amount Δy_(i) for each frameS_(i) according to the selection as follows,

1) if the frame S_(i) is selected as the virtual indirect measuringinstrument of strip performance, that is, the frame S_(i) is providedwith a load cell, calculating the feed-forward adjustment amount Δy_(i)for the frame S_(i) according to the formula 2:

$\begin{matrix}{{{\Delta\; y_{i}} = \frac{\Delta\; h_{i} \times F_{i}}{C_{pi}}},} & (2)\end{matrix}$where Δh_(i) is the thickness deviation of the strip at the entry of theframe S_(i) measured by the thickness gauge. If there is no thicknessgauge provided at the entry of the frame S_(i), the feed-forwardadjustment amount for the frame S_(i) will not be calculated;C_(pi) is the longitudinal rigidity of the frame S_(i);F_(i) is the influence coefficient of the thickness of the strip at theentry of the frame S_(i) on the rolling force of the frame S_(i), whichis an empirical coefficient and obtained through experiments;

2) if the frame S_(i) is not selected as the virtual indirect measuringinstrument of strip performance, that is, the frame S_(i) is notprovided with a load cell, then the value of deformation resistancefluctuation of this frame is that of the previous nearest frame, thatis, Δk_(i)=Δk_(i-1), then calculating the feed-forward adjustment amountΔy_(i) for the frame S_(i) according to the formula 3:

$\begin{matrix}{{{\Delta\; y_{i}} = \frac{{\Delta\; k_{i} \times Q_{i}} + {\Delta\; h_{i} \times F_{i}}}{C_{pi}}},} & (3)\end{matrix}$where Δh_(i) is the thickness deviation of the strip at the entry of theframe S_(i) measured by the thickness gauge. If there is no thicknessgauge provided at the entry of the frame S_(i), then Δh_(i)=0.C_(pi) is the longitudinal rigidity of the frame S_(i);F_(i) is the influence coefficient of the thickness of the strip at theentry of the frame S_(i) on the rolling force of the frame S_(i), whichis an empirical coefficient and obtained through experiments.

In the substep 2) of step 3, if the frame S_(i) is not selected as thevirtual indirect measuring instrument of strip performance, that is, theframe S_(i) is not provided with a load cell but is provided with athickness gauge (1) at the entry thereof, an influence coefficient a_(i)of the deformation resistance on the thickness feed-forward parametercompensation may be added when calculating the feed-forward adjustmentamount of the frames, then calculating the feed-forward adjustmentamount Δy_(i) for the frame S_(i) according to the formulas 4:

$\begin{matrix}{{{\Delta\; y_{i}} = \frac{{b_{i} \times \Delta\; k_{i} \times Q_{i}} + {\Delta\; h_{i} \times F_{i}}}{C_{pi}}},} & (4)\end{matrix}$where b_(i) is the performance feed-forward weighting coefficient of theframe S_(i).

and

$\begin{matrix}{{b_{i} = {a_{i} \times \frac{C_{pi}}{Q_{i}}}},} & (5)\end{matrix}$where a_(i) is the influence coefficient of the deformation resistanceof the frame S_(i) on the thickness feed-forward parameter compensation,which is an empirical coefficient and obtained through experiments.

Selecting the frame S₁ and S₄ as the virtual indirect measuringinstruments of strip performance, and providing a load cell respectivelyon the frame S₁ and S₄, and a thickness gauge respectively at theentries of the frame S₁, S₄ and S₅; calculating the deformationresistance fluctuation of supplied material of the frame S₁ according tothe formula 1:

${{\Delta\; k_{1}} = \frac{\Delta\; P_{1}}{Q_{1}}},{{{\Delta\; k_{4}} = \frac{\Delta\; P_{4}}{Q_{4}}};}$finally, calculating the feed-forward adjustment amounts of the framesS₁, S₂, S₃, S₄ and S₅ respectively,

1) if the frame S₁ is selected as a virtual indirect measuringinstrument of strip performance, calculating the feed-forward adjustmentamount Δy₁ of the frame S₁ according to the formula 2,

${{\Delta\; y_{1}} = \frac{\Delta\; h_{1} \times F_{1}}{C_{p\; 1}}};$

2) if the frame S₂ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₂=Δk₁, then calculating thefeed-forward adjustment amount Δy₂ of the frame S₂ according to theformula 3,

${{\Delta\; y_{2}} = \frac{{\Delta\; k_{2} \times Q_{2}} + {\Delta\; h_{2} \times F_{2}}}{C_{p\; 2}}},$where Δh₂ is the thickness deviation of the strip at the entry of theframe S₂ measured by the thickness gauge;

3) if the frame S₃ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₃=Δk₂, then calculating thefeed-forward adjustment amount Δy₃ of the frame S₃ according to theformula 3,

${{\Delta\; y_{3}} = \frac{{\Delta\; k_{3} \times Q_{3}} + {\Delta\; h_{3} \times F_{3}}}{C_{p\; 3}}},$where because the frame S₃ is not provided with a thickness gauge at theentry thereof, Δh₃=0, thus

${\Delta\; y_{3}} = {\frac{\Delta\; k_{3} \times Q_{3}}{C_{p\; 3}}.}$

4) if the frame S₄ is selected as a virtual indirect measuringinstrument of strip performance, because the frame S₄ is not providedwith a thickness gauge at the entry thereof, the feed-forward adjustmentamount for the frame S₄ will not be calculated;

5) if the frame S₅ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₅=Δk₄, then calculating thefeed-forward adjustment amount Δy₅ of the frame according to the formula3,

${{\Delta\; y_{3}} = \frac{{\Delta\; k_{3} \times Q_{3}} + {\Delta\; h_{3} \times F_{3}}}{C_{p\; 3}}},$where Δh₅ is the thickness deviation of the strip at the entry of theframe S₅ measured by the thickness gauge.

In the present invention, the performance feed-forward thickness controlmethod in a tandem cold mill performs the feed-forward thickness controlthrough the deformation resistance force of the supplied materialsmeasured indirectly, makes measurement on the deformation resistanceforce of each section of the supplied strips through the selectedframes, and when the strip is being rolled in the downstream frames,controls the thickness of the strips by comprehensively considering thethickness and the deformation resistance of the supplied materials. Themethod prevents the effects of the performance fluctuation of thesupplied hot rolled products on the thickness precision during the coldrolling and improves the thickness control precision, which is ofpositive significance to ensure the precision of the thickness offinished products of the strip in the length direction of the entiresteel coil, reducing the fluctuation of the thickness of the finishedproducts of the strip and ensuring stable rolling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the block flow chart of the thickness feed-forward controlmethod in a tandem cold mill in the prior art.

FIG. 2 is the block flow chart of the embodiment 1 of the thicknessfeed-forward control method in a tandem cold mill in the presentinvention.

FIG. 3 is the block flow chart of the embodiment 2 of the thicknessfeed-forward control method in a tandem cold mill in the presentinvention.

FIG. 4 is the block flow chart of the embodiment 3 of the thicknessfeed-forward control method in a tandem cold mill in the presentinvention.

FIG. 5 is the block flow chart of the embodiment 4 of the thicknessfeed-forward control method in a tandem cold mill in the presentinvention.

In the drawings, reference numeral 1 indicates a thickness gauge, andreference numeral 2 indicates a pressure measuring instrument.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be further described in conjunction with thedetailed embodiments below. It should be understood that theseembodiments are only used for illustrating the present invention but notfor limiting the scope thereof. Furthermore, it should be understoodthat upon reviewing the description of the present invention, thoseskilled in the art can make any variation or modification to the presentinvention and these equivalents fall equally into the scope defined bythe appended claims of the application.

Embodiment 1

A performance feed-forward thickness control method in a tandem coldmill comprises the following steps:

step 1, selecting one or more frames as virtual indirect measuringinstrument(s) of strip performance, in which the frame S₁ must be avirtual indirect measuring instrument of strip performance, and athickness gauge 1 is provided at the entry of the frame S₁;

step 2, calculating the value of the deformation resistance fluctuationof supplied materials: providing a load cell 2 on the frames selected asthe indirect measuring instruments for the strip performance, measuringthe rolling force deviation ΔP_(i) caused by the deformation resistancefluctuation of the frame S_(i) via the load cell 2, then calculating thevalue of deformation resistance fluctuation Δk_(i) of supplied materialof the frame S_(i) according to the formula 1:

$\begin{matrix}{{{\Delta\; k_{i}} = \frac{\Delta\; P_{i}}{Q_{i}}},} & (1)\end{matrix}$

where Q_(i) is the influence coefficient of the deformation resistanceon the rolling force of the frame S_(i), which is an empiricalcoefficient and obtained through experiments;

step 3, calculating the feed-forward adjustment amount for each frame:calculating the feed-forward adjustment amount Δy_(i) for each frameS_(i) according to the selection as follows.

1) if the frame S_(i) is selected as the virtual indirect measuringinstrument of strip performance, that is, the frame S_(i) is providedwith a load cell 2, calculating the feed-forward adjustment amountΔy_(i) for the frame S_(i) according to the formula 2:

$\begin{matrix}{{{\Delta\; y_{i}} = \frac{\Delta\; h_{i} \times F_{i}}{C_{p\; i}}},} & (2)\end{matrix}$where Δh_(i) is the thickness deviation of the strip at the entry of theframe S_(i) measured by the thickness gauge 1. If there is no thicknessgauge 1 provided at the entry of the frame S_(i) the feed-forwardadjustment amount Δy_(i) for the frame S_(i) will not be calculated;C_(pi) is the longitudinal rigidity of the frame S_(i);F_(i) is the influence coefficient of the thickness of the strip at theentry of the frame S_(i) on the rolling force of the frame S_(i), whichis an empirical coefficient and obtained through experiments;

-   2) if the frame S_(i) is not selected as the virtual indirect    measuring instrument of strip performance, that is, the frame S_(i)    is not provided with a load cell 2, the value of deformation    resistance fluctuation of this frame is that of the previous nearest    frame, that is, Δk_(i)=Δk_(i-1), then calculating the feed-forward    adjustment amount Δy_(i) for the frame S_(i) according to the    formula 3:

$\begin{matrix}{{{\Delta\; y_{i}} = \frac{{\Delta\; k_{i} \times Q_{i}} + {\Delta\; h_{i} \times F_{i}}}{C_{p\; i}}},} & (3)\end{matrix}$where Δh_(i) is the thickness deviation of the strip at the entry of theframe S_(i) measured by the thickness gauge 1. If there is no thicknessgauge 1 provided at the entry of the frame S_(i), then Δh_(i)=0;C_(pi) is the longitudinal rigidity of the frame S_(i);F_(i) is the influence coefficient of the thickness of the strip at theentry of the frame S_(i) on the rolling force of the frame S_(i) whichis an empirical coefficient and obtained through experiments.

In the feed-forward thickness control method for the performance of atandem cold mill in the present invention, to further improve theaccuracy of thickness control of strips, in the substep 2) of step 3, ifthe frame S_(i) is not selected as the virtual indirect measuringinstrument of strip performance, that is, the frame S_(i) is notprovided with a load cell 2 but is provided with a thickness gauge 1 atthe entry thereof, an influence coefficient a_(i) of the deformationresistance on the thickness feed-forward parameter compensation may beadded when calculating the feed-forward adjustment amount of the frames,then calculating the feed-forward adjustment amount Δy_(i) for eachframe S_(i) according to the formulas 4:

$\begin{matrix}{{{\Delta\; y_{i}} = \frac{{b_{i} \times \Delta\; k_{i} \times Q_{i}} + {\Delta\; h_{i} \times F_{i}}}{C_{p\; i}}},} & (4)\end{matrix}$where b_(i) is the feed-forward weighting coefficient for theperformance of the frame S_(i);

and

$\begin{matrix}{{b_{i} = {a_{i} \times \frac{C_{pi}}{Q_{i}}}},} & (5)\end{matrix}$where a_(i) is the influence coefficient of the deformation resistanceof the frame S_(i) on the thickness feed-forward parameter compensation,which is an empirical coefficient and obtained through experiments.

As shown in FIG. 2, the embodiment describes the performancefeed-forward thickness control method through a thickness control systemof six-roller rolling mill with five frames. In the industrialapplication, the system is divided into a program running area and adata storage area when the PLC controller is operating. The parametersrelated to the thickness control algorithm and the strip informationtable is stored in the data storage area. For the output of thefeed-forward control of the frames S₁˜S₅, selecting the frame S₁ as thevirtual indirect measuring instruments of strip performance, andproviding a load cell 2 on the frame S₁ and a thickness gauge 1respectively at the entries of the frames S₁, S₄ and S₅;

Calculating the deformation resistance fluctuation of supplied materialof the frame S₁ according to the formula 1:

${{\Delta\; k_{1}} = \frac{\Delta\; P_{1}}{Q_{1}}};$and calculating the feed-forward adjustment amount of the frames S₁˜S₅as follows:

1) if the frame S_(i) is selected as a virtual indirect measuringinstrument of strip performance, calculating the feed-forward adjustmentamount Δy₁ of the frame S₁ according to the formula 2,

${{\Delta\; y_{1}} = \frac{\Delta\; h_{1} \times F_{1}}{C_{p\; 1}}};$

2) if the frame S₂ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₂=k₁, then calculating thefeed-forward adjustment amount Δy₂ of the frame S₂ according to theformula 3,

${{\Delta\; y_{2}} = \frac{{\Delta\; k_{2} \times Q_{2}} + {\Delta\; h_{2} \times F_{2}}}{C_{p\; 2}}};$

3) if the frame S₃ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₃=Δk₂, then calculating thefeed-forward adjustment amount Δy₃ of the frame S₃ according to theformula 3,

${{\Delta\; y_{3}} = \frac{{\Delta\; k_{3} \times Q_{3}} + {\Delta\; h_{3} \times F_{3}}}{C_{p\; 3}}},$where because the frame S₃ is not provided with a thickness gauge at theentry thereof, Δh₃=0, thus

${{\Delta\; y_{3}} = \frac{\Delta\; k_{3} \times Q_{3}}{C_{p\; 3}}};$

4) if the frame S₄ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₄=Δk₃, then calculating thefeed-forward adjustment amount Δy₄ of the frame S₄ according to theformula 3,

${{\Delta\; y_{4}} = \frac{{\Delta\; k_{4} \times Q_{4}} + {\Delta\; h_{4} \times F_{4}}}{C_{p\; 4}}},$where because the frame S₃ is not provided with a thickness gauge at theentry thereof, Δh₄=0, thus

${{\Delta\; y_{4}} = \frac{\Delta\; k_{4} \times Q_{4}}{C_{p\; 4}}};$

5) if the frame S₅ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₅=k₄, then calculating thefeed-forward adjustment amount Δy₅ of the frame S₅ according to theformula 3.

${\Delta\; y_{5}} = {\frac{{\Delta\; k_{5} \times Q_{5}} + {\Delta\; h_{5} \times F_{5}}}{C_{p\; 5}}.}$

Embodiment 2

A performance feed-forward thickness control method in tandem cold millis shown in FIG. 3, the difference between the embodiment 2 and 1 liesin that in the embodiment 2, selecting the frame S₁ and S₄ as thevirtual indirect measuring instruments of strip performance, andproviding a load cell 2 respectively on the frame S₁ and S₄, and athickness gauge 1 respectively at the entries of the frame S₁, S₄ (

,

S₂) and S₅; calculating the deformation resistance fluctuation ofsupplied material of the frame S₁ according to the formula 1:

${{\Delta\; k_{1}} = \frac{\Delta\; P_{1}}{Q_{1}}},{{{\Delta\; k_{4}} = \frac{\Delta\; P_{4}}{Q_{4}}};}$finally, calculating the feed-forward adjustment amount of the framesS₁, S₂, S₃, S₄ and S₅ respectively.

1) if the frame S₁ is selected as a virtual indirect measuringinstrument of strip performance, calculating the feed-forward adjustmentamount Δy₁ of the frame S₁ according to the formula 2.

${{\Delta\; y_{1}} = \frac{\Delta\; h_{1} \times F_{1}}{C_{p\; 1}}};$

2) if the frame S₂ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₂=Δk₁, then calculating thefeed-forward adjustment amount Δy₂ of the frame S₂ according to theformula 3,

${{\Delta\; y_{2}} = \frac{{\Delta\; k_{2} \times Q_{2}} + {\Delta\; h_{2} \times F_{2}}}{C_{p\; 2}}},$where Δh₂ is the thickness deviation of the strip at the entry of theframe S₂ measured by the thickness gauge 1;

3) if the frame S₃ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₃=k₂, then calculating thefeed-forward adjustment amount Δy₃ of the frame S₃ according to theformula 3

${{\Delta\; y_{3}} = \frac{{\Delta\; k_{3} \times Q_{3}} + {\Delta\; h_{3} \times F_{3}}}{C_{p\; 3}}},$where because the frame S₃ is not provided with a thickness gauge at theentry thereof, Δh₃=0, thus

${\Delta\; y_{3}} = {\frac{\Delta\; k_{3} \times Q_{3}}{C_{p\; 3}}.}$

4) if the frame S₄ is selected as a virtual indirect measuringinstrument of strip performance, because the frame S₄ is not providedwith a thickness gauge at the entry thereof, the feed-forward adjustmentamount of the frame S₄ will not be calculated;

5) if the frame S₅ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₅=Δk₄, then calculating thefeed-forward adjustment amount Δy₅ of the frame S₅ according to theformula 3,

${{\Delta\; y_{5}} = \frac{{\Delta\; k_{5} \times Q_{5}} + {\Delta\; h_{5} \times F_{5}}}{C_{p\; 5}}},$where Δh₅ is the thickness deviation of the strip at the entry of theframe S₅ measured by the thickness gauge 1.

Embodiment 3

A performance feed-forward thickness control method in a tandem coldmill is shown in FIG. 4, the difference between the embodiment 3 and 1lies in that in the embodiment 3, an influence coefficient of thedeformation resistance on the thickness feed-forward parametercompensation is added when calculating the feed-forward adjustmentamount of the frames:

1) if the frame S₂ is not selected as a virtual indirect measuringinstrument of strip performance, and a thickness gauge 1 is arranged atthe entry of the frame S₂, that is, Δk₂=Δk₁, calculating thefeed-forward adjustment amount Δy₂ of the frame S₂ according to theformula 4 and 5,

${{\Delta\; y_{2}} = \frac{{b_{2} \times \Delta\; k_{2} \times Q_{2}} + {\Delta\; h_{2} \times F_{2}}}{C_{p\; 2}}},$where b₂ is the performance feed-forward weighting coefficient of theframe S₂.

and

${b_{2} = {a_{2} \times \frac{C_{p\; 2}}{Q_{2}}}},$where a₂ is the influence coefficient of the deformation resistance ofthe frame S₂ on the thickness feed-forward parameter compensation, whichis an empirical coefficient and obtained through experiments.

2) if the frame S₅ is not selected as a virtual indirect measuringinstrument of strip performance, and a thickness gauge 1 is arranged atthe entry of the frame S₅ that is, Δk₅=Δk₄, calculating the feed-forwardadjustment amount Δy₅ of the frame S₅ according to the formula 4,

${{\Delta\; y_{5}} = \frac{{b_{5} \times \Delta\; k_{5} \times Q_{5}} + {\Delta\; h_{5} \times F_{5}}}{C_{p\; 5}}},$where b₅ is the performance feed-forward weighting coefficient of theframe S₅.

and

${b_{5} = {a_{5} \times \frac{C_{p\; 5}}{Q_{5}}}},$where a₅ is the influence coefficient of the deformation resistance ofthe frame S₅ on the thickness feed-forward parameter compensation, whichis an empirical coefficient and obtained through experiments.

Embodiment 4

A performance feed-forward thickness control method in a tandem coldmill is shown in FIG. 5, the difference between the embodiment 4 and 2lies in that in the embodiment 4, an influence coefficient of thedeformation resistance on the thickness feed-forward parametercompensation is added when calculating the feed-forward adjustmentamount of the frames:

1) if the frame S₂ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₂=Δk₁, and a thickness gauge1 is arranged at the entry of the frame S₂, calculating the feed-forwardadjustment amount Δy₂ of the frame S₂ according to the formula 4,

${{\Delta\; y_{2}} = \frac{{b_{2} \times \Delta\; k_{2} \times Q_{2}} + {\Delta\; h_{2} \times F_{2}}}{C_{p\; 2}}},$where b₂ is the performance feed-forward weighting coefficient of theframe S₂.

and

${b_{2} = {a_{2} \times \frac{C_{p\; 2}}{Q_{2}}}},$where a₂ is the influence coefficient of the deformation resistance ofthe frame S₂ on the thickness feed-forward parameter compensation, whichis an empirical coefficient and obtained through experiments.

2) if the frame S₅ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₅=k₄, and a thickness gauge1 is arranged at the entry of the frame S₅, calculating the feed-forwardadjustment amount Δy₅ of the frame S₅ according to the formula 4,

${{\Delta\; y_{5}} = \frac{{b_{5} \times \Delta\; k_{5} \times Q_{5}} + {\Delta\; h_{5} \times F_{5}}}{C_{p\; 5}}},$where b₅ is the performance feed-forward weighting coefficient of theframe S₅.

and

${b_{5} = {a_{5} \times \frac{C_{p\; 5}}{Q_{5}}}},$where a₅ is the influence coefficient of the deformation resistance ofthe frame S₅ on the thickness feed-forward parameter compensation, whichis an empirical coefficient and obtained through experiments.

The invention claimed is:
 1. A performance feed-forward thicknesscontrol method for a control system comprising a plurality of framesS_(i) in a tandem cold mill, comprises the following steps: step 1:providing a thickness gauge at the entry of S₁ and selecting S₁ as avirtual indirect measuring instrument for strip performance; step 2:providing a load cell on the frames that are selected as the indirectmeasuring instruments for the strip performance, measuring the rollingforce deviation ΔP_(i) caused by the deformation resistance fluctuationof the frame S_(i) via the load cell, then calculating the value ofdeformation resistance fluctuation Δk_(i) of supplied material of theframe S_(i)according to the formula 1: $\begin{matrix}{{{\Delta\; k_{i}} = \frac{\Delta\; P_{i}}{Q_{i}}},} & (1)\end{matrix}$ where Q_(i) is the influence coefficient of thedeformation resistance on the rolling force of the frame S_(i), which isan empirical coefficient and obtained through experiments; step 3:calculating the feed-forward adjustment amount Δy_(i) for each frameS_(i) according to the selection as follows: substep 1: if the frameS_(i) is selected as the virtual indirect measuring instrument of stripperformance, that is, the frame S_(i) is provided with a load cell,calculating the feed-forward adjustment amount Δy_(i) for the frameS_(i) according to the formula 2: $\begin{matrix}{{{\Delta\; y_{i}} = \frac{\Delta\; h_{i} \times F_{i}}{C_{pi}}},} & (2)\end{matrix}$ where Δh_(i) is the thickness deviation of the strip atthe entry of the frame S_(i) measured by a thickness gauge, if there isno thickness gauge provided at the entry of the frame S_(i), thefeed-forward adjustment amount Δy_(i) for the frame S_(i) will not becalculated; C_(pi) is the longitudinal rigidity of the frame S_(i);F_(i) is the influence coefficient of the thickness of the strip at theentry of the frame S_(i) on the rolling force of the frame S_(i) whichis an empirical coefficient and obtained through experiments; andsubstep 2: if the frame S_(i) is not selected as the virtual indirectmeasuring instrument of strip performance, that is, the frame S_(i) isnot provided with a load cell, the value of deformation resistancefluctuation of this frame is that of the previous nearest frame, thatis, Δk_(i)=Δk_(i-1), then calculating the feed-forward adjustment amountΔy_(i) for the frame S_(i) according to the formula 3: $\begin{matrix}{{{\Delta\; y_{i}} = \frac{{\Delta\; k_{i} \times Q_{i}} + {\Delta\; h_{i} \times F_{i}}}{C_{p\; i}}},} & (3)\end{matrix}$ where Δh_(i) is the thickness deviation of the strip atthe entry of the frame S_(i) measured by a thickness gauge, if there isno thickness gauge provided at the entry of the frame S_(i) , thenΔh_(i)=0; C_(pi) is the longitudinal rigidity of the frame S_(i); F_(i)is the influence coefficient of the thickness of the strip at the entryof the frame S_(i) on the rolling force of the frame S_(i), which is anempirical coefficient and obtained through experiments, and wherein thecontrol system uses the calculated feed-forward adjustment to controlthe thickness of the thickness of cold rolled strips.
 2. The performancefeed-forward thickness control method in a tandem cold mill according toclaim 1, characterized in that in the substep 2) of step 3, if the frameS_(i) is not selected as the virtual indirect measuring instrument ofstrip performance, that is, the frame S_(i) is not provided with a loadcell but is provided with a thickness gauge at the entry thereof, aninfluence coefficient α_(i) of the deformation resistance on thethickness feed-forward parameter compensation is added when calculatingthe feed-forward adjustment amount of the frame, then calculating thefeed-forward adjustment amount Δy_(i) for the frame S_(i) according tothe formulas 4 and 5: $\begin{matrix}{{{\Delta\; y_{i}} = \frac{{b_{i} \times \Delta\; k_{i} \times Q_{i}} + {\Delta\; h_{i} \times F_{i}}}{C_{p\; i}}},} & (4)\end{matrix}$ where b_(i) is the performance feed-forward weightingcoefficient of the frame S_(i), and $\begin{matrix}{{b_{i} = {a_{i} \times \frac{C_{p\; i}}{Q_{i}}}},} & (5)\end{matrix}$ where α_(i) is the influence coefficient of thedeformation resistance of the frame S_(i) on the thickness feed-forwardparameter compensation, which is an empirical coefficient and obtainedthrough experiments.
 3. The performance feed-forward thickness controlmethod in a tandem cold mill according to claim 1, characterized in thatthe frames S₁ and S₄ are selected as the virtual indirect measuringinstruments of strip performance, and providing a load cell respectivelyon the frame S₁ and S₄, and a thickness gauge respectively at theentries of the frame S₁, S₄ and S₅; calculating the deformationresistance fluctuation of supplied material of the frame S₁ according tothe formula 1:${{\Delta\; k_{1}} = \frac{\Delta\; P_{1}}{Q_{1}}},{{{\Delta\; k_{4}} = \frac{\Delta\; P_{4}}{Q_{4}}};}$finally, calculating the feed-forward adjustment amounts of the framesS₁, S₂, S₃, S₄ and S₅ respectively, 1) if the frame S₁ is selected as avirtual indirect measuring instrument of strip performance, calculatingthe feed-forward adjustment amount Δy₁ of the frame S₁ according to theformula 2,${{\Delta\; y_{1}} = \frac{\Delta\; h_{1} \times F_{1}}{C_{p\; 1}}};$ 2)if the frame S₂ is not selected as a virtual indirect measuringinstrument of strip performance, that is, Δk₂=Δk₁, then calculating thefeed-forward adjustment amount Δy₂ of the frame S₂ according to theformula 3,${{\Delta\; y_{2}} = \frac{{\Delta\; k_{2} \times Q_{2}} + {\Delta\; h_{2} \times F_{2}}}{C_{p\; 2}}},$ where Δh₂ is the thickness deviation of the strip at the entry of theframe S₂ measured by the thickness gauge; 3) if the frame S₃ is notselected as a virtual indirect measuring instrument of stripperformance, that is, Δk₃=Δk₂, then calculating the feed-forwardadjustment amount Δy₃ of the frame S₃ according to the formula 3,${{\Delta\; y_{3}} = \frac{{\Delta\; k_{3} \times Q_{3}} + {\Delta\; h_{3} \times F_{3}}}{C_{p\; 3}}},$ where because the frame S₃ is not provided with a thickness gauge atthe entry thereof, Δh₃=0, thus${{\Delta\; y_{3}} = \frac{\Delta\; k_{3} \times Q_{3}}{C_{p\; 3}}};$ 4)if the frame S ₄ is selected as a virtual indirect measuring instrumentof strip performance, because the frame S₄ is not provided with athickness gauge at the entry thereof, the feed-forward adjustment amountof the frame S₄ will not be calculated; 5) if the frame S₅ is notselected as a virtual indirect measuring instrument of stripperformance, that is, Δk₅=Δk₄, then calculating the feed-forwardadjustment amount Δy₅ of the frame S₅ according to the formula 3,${{\Delta\; y_{5}} = \frac{{\Delta\; k_{5} \times Q_{5}} + {\Delta\; h_{5} \times F_{5}}}{C_{p\; 5}}},$ where Δh₅ is the thickness deviation of the strip at the entry of theframe S₅ measured by the thickness gauge.
 4. The performancefeed-forward thickness control method of claim 1, wherein step 1 furthercomprises selecting one or more additional frames as virtual indirectmeasuring instrument(s) for strip performance.